Optical tracking of spherical micro-objects in spatially periodic interference fields

We present a new method that provides precise detection of micro-object position with respect to a spatially periodic illumination field. Altering the mutual position of the object and the illumination field causes that a pattern of scattered light detected perpendicularly by a CCD camera changes. We present a procedure how to employ this pattern changes to track micrometer-size object in the standing wave and how to apply this method to optical tracking of Brownian particle even in periodic illumination field in motion. (c) 2007 Optical Society of America.